May 5, 2017, by Tim Radford
A microbe found in rice fields is helping to convert methane gas into biofuels.
Image: Yamanaka Tamaki via Flickr
Ingenuity in laboratories worldwide is harnessing microbes, water and hot air to produce different types of renewable energy from greenhouse gas.
LONDON, 5 May, 2017 – Swiss scientists have found a way to turn the potent greenhouse gas methane into the fuel methanol – with help from water and a simple catalyst.
Meanwhile, US researchers have tested a way to convert methane into biofuels, specialised chemicals or even cattle feed with help from one microbe from rice fields and another from a Siberian lake.
And in Norway, engineers are testing something seemingly simpler: they want to exploit air as a battery that could store surplus renewable energy.
All three studies are examples of the astonishing levels of ingenuity and invention repeatedly demonstrated in the world’s laboratories as chemists, engineers and microbiologists focus on the great energy challenge.
Greenhouse gas emissions
They are all seeking ways to reduce greenhouse gas emissions from fossil fuel combustion, by recycling them, by being more efficient, by eliminating waste, and by harnessing sunlight, air and water to improve on nature.
Any of these technologies could one day make a powerful contribution to energy efficiency, And although all of them are a long way from routine exploitation, they demonstrate that, over and over again, researchers are bringing new ideas to a problem at least as old as the Industrial Revolution.
One inspiration comes from methane, a greenhouse gas that is more shortlived in the atmosphere than carbon dioxide, but also many times more efficient in its contribution to global warming.
It is known as “natural” gas, but farming – from rice fields to cattle pastures – produces huge quantities of methane, and so do fossil fuel sources.
“We take a waste product that is normally an expense and upgrade it to microbial biomass that can be used to make fuel, fertiliser, animal feed, chemicals and other products”
Researchers from the Swiss Federal Institute of Technology, known as ETH Zurich, report in Science journal that they have devised a catalytic system based on copper-containing zeolites, with an unexpected property.
It can turn methane, with the chemical formula CH4, into liquid methanol,(CH3OH,) by exploiting the oxygen in water, and it can do so with 97% efficiency.
It remains just that − a process, and so far an expensive one “only economically feasible at very large scale”, they say, and not something engineers could tap into at, for instance, an ocean or a desert oil drilling rig, where oilmen still “flare” waste methane from the wells.
But a team from the Pacific Northwest National Laboratory (PNNL) in Washington state, US, have something that could be more portable: a bio-reactor that could turn methane captured at oil fields and at farmyards into a deep-green, energy-rich, gelatinous substance that could be exploited for a range of products.
This process depends on two microbes not normally found in the same place, they write in Bioresource Technology journal.
One is known as Methylomicrobium alcaliphilum 20Z and it feeds on methane at landfill sites and rice paddy fields. The other is known only as Synechococcus 7002 and it lives in a Siberian lake, using light and carbon dioxide to release oxygen.
Together, the Washington scientists say, they engaged in “productive metabolic coupling” to produce something new.
“We take a waste product that is normally an expense and upgrade it to microbial biomass that can be used to make fuel, fertiliser, animal feed, chemicals and other products,” says Hans Bernstein, a chemical and biological engineer who is a member of the PNNL research team.
“The two organisms complement each other, support each other. We have created an adaptable biotechnology platform with microbes that are genetically tractable for the synthesis of biofuels and biochemicals.”
In Norway, engineers from the SINTEF energy enterprise have examined another approach to the power game. They are partners in a European project to find ways to store energy underground.
And they want to put the energy back into circulation with a battery based simply on hot air. This is air heated and compressed by surplus energy from wind and solar plant, and then stored in a subterranean cavern.
The flow of hot air passes through a portal cavern filled with crushed rock, and heats up the rock. The cool compressed air is stored in a second cavern and, when needed, it is released through the hot rocks.
It is then piped through a turbine to generate electricity to meet peak demand, or demand when solar power cells cannot deliver, or at any time when the wind drops and the turbine blades fall still.
There is a catch, however. To excavate subterranean storage for such a battery would be ruinously expensive.
But Giovanni Perillo, a research scientist who is the project manager, says: “We regard disused tunnels and mineshafts as potential storage sites, and Norway has those in plenty.
“The more of the heat of compression that the air has retained when it is released from the store, the more work it can perform as it passes through the gas turbine. And we think that we will be able to conserve more of that heat than current storage technology can, thus increasing the net efficiency.” – Climate News Network
Tim Radford, a founding editor of Climate News Network, worked for The Guardian for 32 years, for most of that time as science editor. He has been covering climate change since 1988.